1. Field of the Invention
This invention relates generally to video camera systems for commercial aircraft, and more particularly relates to a closed circuit television system having one or more cameras providing multiple fields of view exterior to the aircraft to provide video to existing passenger entertainment video systems.
2. Description of Related Art
Commercial airlines now provide in flight entertainment (IFE) systems with video on demand (VOD) and digital audio/video on demand (AVOD), allowing airline passengers to choose a video or audio selection for their in flight entertainment. One video option that can be made available is a view from a video camera of the environment outside the aircraft during flight. One conventional exterior video camera system, for example, provided camera views through a window provided forward of the nose wheel.
A variety of views can also be made available in a closed circuit television from multiple video cameras, as is disclosed in U.S. Pat. No. 5,574,497, which is incorporated by reference in its entirety herein. Two cameras were housed in a single sealed module, with one camera directed approximately forward toward the horizon, and a second camera directed downward, as is illustrated in FIGS. 1a and 1b depicting the general arrangement of camera views in the prior art system. Each camera in this system employed a CCD imager configured as either a camera head unit (CHU) remotely mounted in the aircraft structure, and a companion electronics unit designated as a camera control unit (CCU) located in an electronics and equipment (E&E) bay of the aircraft, or as a single module with the CHU and CCU integrated as a camera module unit (CMU). As is illustrated in FIGS. 1a and 1b, the camera housing unit 3 is structurally integrated into the fuselage skin 1. This structural integration includes an optical grade window 5, and the camera head units 4, 7. The installation area shown is located in a structural bay bounded by frames 2, 8. When the remote mounting of the CCU in the E&E bay is eliminated, cable weight is reduced by over 95%, yielding an overall weight savings in excess of 40 lbs. for a typical B-747-400 aircraft installation.
The fields of view available from such conventional video cameras were interfaced to the onboard video entertainment systems as an analog signal, essentially allowing the passenger to select the fixed fields of view provided by the video cameras mounted on board the aircraft. A typical field of view arrangement available with the prior art dual camera design is shown in FIG. 2. The two fields of view are: 1) Forward Looking, described by angle FBG, and 2) Downward Looking, described by angle HBI. The camera fields of view are aligned along two references; the forward looking camera along a horizontal reference described by line AC, and the downward looking camera long a vertical reference described by line DE, which is perpendicular to the horizontal reference. This optical combination produces an angular field of view range from 7.5° (H) by 5.75° (V) to 3.8° (H) by 2.8° (V). The lens combinations described provide the optical characteristics required in order to minimize the size of the structural window 5, shown in FIG. 1b. However, changing of the fields of view of a video camera such as by panning the camera resulted in a change of the field of view for each passenger viewing the selected camera video view, and individual passenger control for each passenger to select different fields of view was not possible.
It would be desirable to provide a closed circuit television system making multiple fields of view available for selection by passengers on the aircraft, either from a single video frame from a single video camera, or from multiple video cameras providing views individually selectable by passengers on the aircraft. The present invention meets these needs.